Task Generator Util

task-generator.js

const yieldToMain = () =>
  new Promise((resolve) => {
    requestAnimationFrame(() => {
      setTimeout(resolve);
    });
  });

class Task {
  state = "IDLE";

  constructor(runnable, options) {
    this.runnable = runnable;
    this.options = options;
  }

  abort() {
    this.state = "ABORTED";
  }

  async run() {
    const { state: initialState } = this;
    if (initialState === "ABORTED") {
      throw new Error("cannot run aborted task");
    } else if (initialState === "COMPLETED") {
      throw new Error("cannot re-run completed task");
    }
    this.state = "RUNNING";
    const { options, runnable } = this;
    let iteratorValue;
    try {
      while (true) {
        const { state } = this;
        if (!(state === "RUNNING")) {
          break;
        }
        const iteratorResult = runnable.next(iteratorValue);
        iteratorValue = await iteratorResult.value;
        if (options?.callback) {
          options.callback(iteratorValue);
        }
        if (iteratorResult.done) {
          this.state = "COMPLETED";
          break;
        }
      }
    } finally {
      if (options?.onFinished) {
        options.onFinished({ state: this.state });
      }
    }
  }
}
// Sample usage
const doSomeTask = (id) => {
  console.log(`task ${id}  is done`);
};
const abortIfTheTaskRunsMoreThanASec = (task) => {
  setTimeout(() => {
    task.abort();
  }, 1000);
};
const wait = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
const task = new Task(
  (function* () {
    doSomeTask(1);
    yield yieldToMain();
    yield wait(500);
    doSomeTask(2);
    yield wait(500);
    doSomeTask(3);
  })(),
  {
    onFinished: () => console.log("finished before running task 3"),
  }
);
task.run();
abortIfTheTaskRunsMoreThanASec(task);